Ultraviolet particle coating systems and processes

Abstract

Particle coating processes and systems employ UV curable materials to form tack-free surfaces rapidly. By applying UV curable compositions on well suspended particles a UV particle coating technology enables a scalable process of coating fine particles at desirable coating thicknesses with a wide spectrum of obtainable properties. Processes in accordance with the present invention decouple the particle suspension and film formation steps, enabling ample time to first deliver evenly the coating materials to the particle surfaces, followed by rapid polymerization/curing reaction induced by the UV light to rapidly create tack-free surfaces, thus preventing particles agglomeration while achieving uniform and thin-layer coating.

1 . A method of coating at least one particle comprising the steps of: 
 introducing at least one UV curable composition onto a suspended particle, and    curing said composition with UV irradiation.    
   
   
       2 . The method according to  claim 1  comprising suspending at least one particle in a particle coating device.  
   
   
       3 . The method according to  claim 2  said particle coating device selected from the group comprising fluidized coaters, drum coaters, and tumbling coaters.  
   
   
       4 . The method according to  claim 1  further comprising performing the introducing step in a suspension media selected from the group comprising air, nitrogen and carbon dioxide.  
   
   
       5 . The method according to  claim 4  the suspension media comprising non-oxygen containing media.  
   
   
       6 . The method according to claim further comprising the step of applying a vacuum.  
   
   
       7 . The method according to  claim 1  wherein said method is performed at least in part in a coating apparatus modified for application of UV light by providing at least one quartz window in said coater.  
   
   
       8 . The method according to  claim 1  comprising atomizing at least one UV curable liquid composition through a spray nozzle, introducing said atomized liquid into an environment containing fluidized particles and wetting said fluidized solid particulates with said atomized liquid.  
   
   
       9 . The method according to  claim 1  comprising feeding said UV curable composition into a fluidized bed, exposing the composition to said UV light for a selected period of time, permitting a ratio of UV curable composition to reach a target value and stopping the feed of the UV curable composition once the target value is reached.  
   
   
       10 . The method according to  claim 1  said UV curable composition comprising a liquid.  
   
   
       11 . The method according to  claim 1  said UV curable composition selected from the group comprising a free radical system and an ionic system.  
   
   
       12 . The method according to  claim 1  said UV curable composition comprising at least one monomer and at least one photoinitiator.  
   
   
       13 . The method according to  claim 12 , said at least one monomer comprising an acrylate.  
   
   
       14 . The method according to  claim 12  said photoinitiator selected from the group consisting of α-hydroxylketone, α-aminoketone, mono acyl phosphine and bis acyl phosphine.  
   
   
       15 . The method according to  claim 12  said monomer selected from the group consisting of multi-functional vinyl ethers, multi-functional epoxides, hybrids of vinyl ether and epoxide and cyclic monomers.  
   
   
       16 . The method according to  claim 12  said photoinitiator selected from the group consisting of iodonium salts, sulfonium salts bearing at least one aromatic or other resonance stabilizing chromophore, and ferrocenium salts.  
   
   
       17 . The method according to  claim 12  further comprising at least one reactive diluent.  
   
   
       18 . A system adapted to coat particles comprising a coater having a product vessel, at least one UV light source positioned to irradiate particles in said product vessel with UV light, a port for introducing a UV curable composition into said product vessel and at least one air flow.  
   
   
       19 . A system according to  claim 18  said coater comprising a fluidizing coater.  
   
   
       20 . A system according to  claim 18  said coater selected from the group consisting of a fluidized bed, rotating fluidized bed, magnetic assist impact coater, drum coater, free fall coater and spin coaters.  
   
   
       21 . A system according to  claim 18 , said UV light source positioned outside of said coater and said coater comprising a window to admit UV light from said UV light source.  
   
   
       22 . A system according to  claim 21 , said window comprising quartz glass.  
   
   
       23 . A method of coating at least one particle comprising the steps of: 
 contacting at least one particle to be coated with at least one UV curable composition and curing said composition with UV irradiation.    
   
   
       24 . A method according to  claim 23  comprising blending said at least one particle with at least one UV curable powder.  
   
   
       25 . A method according to  claim 24  comprising introducing a blended mixture of said at least one particle and at least one UV curable powder into a coating device.